Sound proofing alternative..

[Defy Belief]

Hi guys i've came from a car audio background and there were always cheaper alternatives to sound deadening back then, instead of paying loads for the top brand proofing, can any of you guys recommend a alternative to decrease sound coming from my pc?

Currently got a lot of capacitor whine, so I will be completely covering the side of my case (NZXT enthusiast) as the side fan isn't used and the gpu sits right there so the noise is loud.